IS 13452 (Part 5) :2003 \\ mm \n J-( m Wwlh A \ Ici?dq"l Indian Standard CHEMICAL ANALYSIS OF FERROCHROMIUM PART 5 DETERMINATION OF CHROMIUM IN HIGH CARBON FERROCHROMIUM/CHARGECHROME BY DICHROMATETITRATION (First Revision ) Ics 77.100 0 BIS 2003 BUREAU MANAK OF BHAVAN, INDIAN STANDARDS ZAFAR MARG 9 BAHADUR SHAH NEW DELHI 110002 .4prii 2003 Price Group 1 Methods of Chemical Analysis of Ferrous Metals Sectional Committee, MTD 2 FOREWORD This Indian Standard (Part 5) (First Revision) was adopted by the Bureau of Indian Standards, after the draft finalized by the Methods of Chemical Analysis of Ferrous Metals Sectional Committee had been approved by the Metallurgical Engineering Division Council. This Standard (Part 5) covers the method for determination of chromium in high carbon ferrochromium/ chargechrome by Bichromate titration, the other parts in this series are: (Part (Part (Part (Part 1): 2): 3): 4): 1992 1992 1992 1992 Determination of silicon in high carbon ferrochromium by gravimetric method Determination of silicon in low carbon ferrochromium by gravimetric method Determination of phosphorus in low carbon ferrochromium by gravimetric method Determination of total sulphur in low carbon and high carbon ferrochromium by direct combusion method Determination of chromium in low carbon ferrochromium Determination of phosphorus in ferrochromium/chargechrome by alkalimetric method (Part 6) :1997 (Part 7): 2003 In this revision, major modifications are as follows: a) b) Scope of the method has been modified by lowering the limit for determination of chromium from 60 to 50 percent (Range from 50 to 70 percent). Procedure has been modified by titrating the excess ferrous ammonium sulphate by standard potassium bichromate solution instead of standard potassium permanganate solution. In reporting the result of a test or analysis made in accordance with this standard, if the final value observed or calculated, is to be rounded off, it shall be done in accordance with IS 2: 1960 `Rules for rounding off numerical values (revised)'. IS 13452 (Part 5): 2003 Indian Standard CHEMICAL ANALYSIS OF FERROCHROMIUM PART 5 DETERMINATION OF CHROMIUM IN HIGH CARBON FERROCHROMIUWCHARGECHROME BY DICHROMATETITRATION (First Revision ) 1 SCOPE 5.2 Reagents 5.2.1 Sodium Peroxide, This standard (Part 5) describes the method for determination of chromium in the range from 50 to 70 percent (containing carbon above 1 percent). 2 REFERENCES The standards listed below contain provisions which through reference in this text, constitute provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below: IS No. solid. Acid, 5 percent 5.2.2 Dilute Sulphuric 20 percent (v/v). (v/v), 5.2.3 Ammonium Persulphate, solid. 5.2.4 Silver Nitrate Solution, 1 percent (w/v). 5.2.5 Phosphoric Acid, rd = 1.75 or 88 percent. 5.2.6 Potassium Permanganate 5.2.7 Dilute Hydrochloric Solution, 25 gll. Acid, 1:1. 5.2.8 Ferrous Ammonium Sulphate Solution, 0.1 N. 5.2.8.1 Dissolve 39.2 g of pure ferrous ammonium 266:1993 1070:1992 1472:1977 Title Sulphuric acid (third revision) Reagent grade water (third revision) Methods of sampling of ferroalloys for determination of chemical composition (first revision) sulphate FeSOJNHJ2 SOd.6H20 in 500 ml of dilute sulphuric acid (5 percent) in a 1-litre volumetric flask and make up to the mark with dilute sulphuric acid (5: 95). 5.2.9 Standard Potassium Bichromate Solution, 0.1 N. 5.2.9.1 Dry potassium bichromate in an oven at 105 to 110"C for one and a half hours, cool in a desiccator. Weigh exactly 4.903 5g. Dissolve in water and transfer to 1-litre volumetric flask, dilute volume and mix. 5.2.10 Sodium Diphenylamine Solution, 0.2 percent (m/v). 5.2.10.1 Sulphonate Indicator 3 SAMPLING The sample shall be drawn and prepared in accordance with IS 1472. 4 QUALITY OF REAGENTS Unless specified otherwise analytical grade reagents and distilled water (see IS 1070) shall be employed for the test. 5 DETERMINATION OF CHROMIUM Dissolve 0.2 g of sodium diphenylamine sulphonate in 100 ml hot distilled water. 5.2.11 Sodium Chloride Solution, 10 percent (w/v). 5.2.12 Concentrated Sulphuric Acid, rd = 1.84 , 5.1 Outline of the Method The sample is fused with sodium peroxide, leached in water and acidified with sulphuric acid. Chromium is oxidized to bichromate by ammonium persulphate in the presence of silver nitrate. The chromium in solution is determined by adding excess of ferrous ammonium sulphate solution and back titrated to a purple end point with standard bichromate solution using sodium diphenylamine sulphonate as indicator to a purple end point. (conforming to IS 266). Take 5.2.13 Phosphoric and Su~huricAcidA4Mure-- 1200 ml of distilled water in a 2-litre capacity flat bottomed flask and to it add 400 ml of concentrated phosphoric acid followed by 400 ml of concentrated sulphuric acid and cool it under tap. 5.3 Procedure 5.3.1 Weigh 0.5 g of finely ground and dried sample in a nickel crucible. Mix well with about 8 g of sodium I IS 13452 (Part 5) :2003 peroxide. Cover with an additional 1 g of sodium peroxide, Heat carefully over a low temperature and finally fuse the mass over a flame till completely fused. 5.3.2 Cool the melt. Place the crucible in a 500 ml beaker and dissolve . Remove the crucible and wash with water any particles adhering to the crucible. Add dilute sulphuric acid until it is acidic. Add fitrther 30 ml and boil for 5 to 10 min. 5.3.3 Add 4 to 5 drops of KMnOA solution (25 g/1) if manganese is not present. Then add 10 ml of silver nitrate solution, warm to about 70 to 80°C and add about 4 to 5 g of ammonium persulphate. Keep on warm condition about 5 min and boil the solution for 10 min. If perrnanganate colour does not develop then add further 4 to 5 g of ammonium persulphate and boil. Continue boiling for about 30 min to destroy excess ammonium persulphate. Add 20 ml of NaCl solution (10 percent w/v) and again boil for 5 to 10 min till oxides of manganese or any permanganate disappears. 5.3.4 Cool the solution (see 5.3.3) to room temperature. Dilute to 350 ml. Add known quantity of ferrous ammonium sulphate till the colour is green and add an excess of 5 ml. Add 10 ml acid mixture followed by 5 to 10 drops of sodium diphenylamine sulphonate indicator and dilute to about 400 ml with distilled water. 5.3.5 Titrate (see 5.3.4) the excess ferrous ammonium sulphate with standard potassium bichromate solution to a purple end point. 5.3.6 Blank Run a blank determination following the procedure and using the same amount of all the reagents and titrate with standard bichromate solution using sodium diphenylamine sulphonate as indicator to a purple end point. 5.3.7 Calculation Chromium, by mass where VI = volume, in ml, of potassium bichromate solution required for ferrous ammonium sulphate used; Vz = volume, solution N M in ml of potassium bichromate required for the back titration; bichromate; and percent . (~-v2)Nxo.01734 M xloo = normality of potassium = mass, in g, of the sample taken. NOTE -- If vanadium content in the material is more than 0.3 percent, use potassium permanganate, solution in place of potassium bichromate solution. 2 Bureau of Indian Standards BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promote harmonious development of the activities of standardization, marking and quality certification of goods and attending to connected matters in the country. Copyright BIS has the copyright of all its publications. No part of these publications may be reproduced in any form without the prior permission in writing of BIS. This does not preclude the free use, in the course" of implementing the standard, of necessary details, such as symbols and sizes, type or grade designations. Enquiries relating to copyright be addressed to the Director (Publications), BIS. Review of Indian Standards Amendments are issued to standards as the need arises on the basis of comments. 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